Control circuit for controlling a uv light source

Abstract

A control circuit for controlling a UV light source configured to emit UV light into a purifying chamber of a device for purifying a fluid, the control circuit comprising a driver configured to provide the UV light source with a drive current; a fluid flow sensor configured to determine whether a flow of a fluid through the purifying chamber is present and generate a flow signal indicative thereof; a light sensor configured to measure radiant flux of light emitted from the UV light source and to generate a radiant flux signal comprising data pertaining to the measured radiant flux; a memory comprising a reference radiant flux; and a processor configured to: activate the UV light source upon the flow signal being indicative of presence of flow of fluid through the purifying chamber, during the UV light source being active: determine the drive current for the driver based on the measured radiant flux comprised in the radiant flux signal and the reference radiant flux.

1 . A control circuit for controlling a UV light source configured to emit UV light into a purifying chamber of a device for purifying a fluid, the control circuit comprising:
 a driver configured to provide the UV light source with a drive current;   a fluid flow sensor configured to determine whether a flow of a fluid through the purifying chamber is present and generate a flow signal indicative thereof;   a light sensor configured to measure radiant flux of light emitted from the UV light source before the light emitted from the UV light source ( 204 ) has entered the purifying chamber and to generate a radiant flux signal comprising data pertaining to the measured radiant flux;   a memory comprising a reference radiant flux; and   a processor configured to:
 upon the flow signal being indicative of presence of flow of fluid through the purifying chamber, activate the UV light source, 
 during the UV light source being activated due to presence of flow of fluid through the purifying chamber, determine the drive current for the driver based on the measured radiant flux comprised in the radiant flux signal and the reference radiant flux; and 
 upon the flow signal being indicative of non-presence of flow of fluid through the purifying chamber, instruct the driver to apply a drive current below a threshold to the UV-light source, wherein the threshold is set so that the radiant flux of UV-light emitted from the UV light source is ≤5% of a maximum radiant flux of UV-light emitted from the UV light source. 
   
     
     
         2 . The control circuit according to  claim 1 , wherein the processor is configured to determine the drive current for the driver by determining a degradation of the UV-light source based on the measured radiant flux comprised in the radiant flux signal and the reference radiant flux, and determine the drive current for the driver based on the degradation of the UV-light source. 
     
     
         3 . (canceled) 
     
     
         4 . The control circuit ( 100 ) according to  claim 1 , wherein the processor is configured to:
 determine a time period of non-presence of flow of fluid through the purifying chamber, and   upon a length of the time period of non-presence of flow of fluid through the purifying chamber is above a threshold, activate the UV light source.   
     
     
         5 . The control circuit according to  claim 1 , wherein the fluid flow sensor is further configured to measure a flow rate of a fluid flowing through the purifying chamber, wherein the flow signal comprises data pertaining to the measured flow rate, and wherein the processor is further configured to determine the drive current for the driver based on the measured flow rate comprised in the flow signal. 
     
     
         6 . The control circuit according to  claim 1 , wherein the light sensor is configured to measure UV-C light radiant flux and wherein the reference radiant flux is a UV-C light reference radiant flux. 
     
     
         7 . The control circuit according to  claim 1 , wherein the UV light source comprises one or more UV LEDs. 
     
     
         8 . The control circuit according to  claim 7 , further comprising a temperature sensor configured to measure a temperature of a UV LED and generate a temperature signal, wherein the processor is configured to, upon the temperature signal being indicative that the temperature of the LED is above a predetermined temperature threshold, generate a LED overheat signal. 
     
     
         9 . The control circuit according to  claim 1 , wherein the processor is configured to, upon the radiant flux signal being indicative that the measured radiant flux is below a predetermined radiant flux threshold, generate a UV light source failure signal. 
     
     
         10 . The control circuit according to  claim 9 , wherein the predetermined radiant flux threshold is a factory set threshold. 
     
     
         11 . A device for purifying a fluid, the device comprising:
 a purifying chamber having a fluid inlet and a fluid outlet for allowing a flow of fluid to be purified to flow there through;   a UV light source configured to emit UV light into the purifying chamber; and   a control circuit according to  claim 1 , configured to control the UV light source.   
     
     
         12 . A method for controlling a UV light source configured to emit UV light into a purifying chamber of a device for purifying a fluid, the method comprising:
 determining whether a flow of a fluid through the purifying chamber is present;   upon determining presence of flow of fluid through the purifying chamber activate the UV light source; and   during the UV light source being active:
 measure a radiant flux being emitted from the UV light source before the light emitted from the UV light source has entered the purifying chamber, 
 compare the measured radiant flux with a reference radiant flux, and 
 adjust a drive current of the UV light source based on the comparison; and 
   upon determining non-presence of flow of fluid through the purifying chamber applying a drive current below a threshold to the UV light source, wherein the threshold is set so that the radiant flux of UV-light emitted from the UV light source is ≤5% of a maximum radiant flux of UV-light emitted from the UV light source.   
     
     
         13 . (canceled) 
     
     
         14 . The method according to  claim 12 , further comprising:
 determining a time period of non-presence of flow of fluid through the purifying chamber, and   upon a length of the time period of non-presence of flow of fluid through the purifying chamber being above a threshold, activating the UV light source for a time period of 1-5 seconds.   
     
     
         15 . The method according to  claim 12 , wherein the step of determining whether a flow of a fluid through the purifying chamber is present comprises measuring a flow rate of the fluid flowing through the purifying chamber, wherein the method further comprises adjusting the drive current of the UV light source based on the measured flow rate. 
     
     
         16 . The method according to  claim 12 , wherein the step of measuring a radiant flux being emitted from the UV light source comprises measuring a UV-C light radiant flux and wherein the reference radiant flux is a UV-C light reference radiant flux. 
     
     
         17 . The method according to  claim 12 , further comprising measuring a temperature of a LED of the UV light source, upon the measured temperature being above a predetermined threshold generate a LED overheat signal. 
     
     
         18 . The method according to  claim 12 , further comprising upon the measured radiant flux being below a predetermined threshold generate a UV light source failure signal. 
     
     
         19 . A non-transitory computer readable recording medium comprising program code portions configured to perform the method according to  claim 12  when executed on the processor comprised in the control circuit of  claim 1 .